This application relates generally to geophysical exploration, and more specifically to seismic data acquisition and sensor technologies. In particular, the application relates to sensor systems for marine seismic surveys, including, but not limited to, ocean bottom cables and autonomous seismic node applications.
Seismic survey technologies are commonly used to explore and develop resources for the petrochemical industry. Petrochemical products are ubiquitous in the modern economy, and can be found in everything from oil and gasoline to medical devices, children's toys, and a wide range of other everyday household items. To meet the continuing demand for these products, oil and gas reserves must be accurately located and surveyed, so that these important resources can be effectively managed. As a result, there is an ongoing need for new seismic sensor systems and more advanced exploration technologies.
Scientists and engineers typically utilize seismic wave-based exploration techniques to locate new oil and gas reservoirs, and to survey and manage existing reserves over time. Seismic surveys are performed by deploying an array of seismic sensors or receivers over the region of interest, and monitoring the response to controlled emission of seismic energy via seismic sources such as vibrators and air gun arrays, or explosive detonations. The response depends upon the seismic energy reflected from subsurface structures, allowing the corresponding geological features to be imaged, including mineral reservoirs and other underground structures of interest.
Marine seismic surveys may proceed by towing an array of seismic sensors or receivers behind a survey vessel, with the receivers distributed along one or more streamer cables. A set of air guns or other seismic sources is used to generate seismic energy that propagates down through the water column to the ocean floor (or other bottom surface). A portion of the seismic energy penetrates the ocean floor and is reflected from subsurface structures, then returns back through the water column to be detected in the streamer array. Seismic receivers can also be disposed along ocean-bottom cables, or provided in the form of individual, autonomous seismic nodes distributed on the seabed.
Typical seismic receivers include pressure sensors and particle motion detectors, which can be provided as individual sensor components, or combined together with both sensor types located in close proximity within a receiver module or seismic node. For example, a set of pressure sensors can be configured in a hydrophone array, and adapted to record scalar pressure measurements of the seismic wavefield propagating through the water column or other seismic medium. Particle motion sensors include accelerometers and geophones, which can be configured to provide single-axis or three-dimensional vector velocity measurements that characterize motion of the medium in response to propagating seismic waves.
Geophysical data pertaining to the subsurface structures is acquired by observing the reflected seismic energy with an array of such receiver components. The observed seismic signals are used to generate a seismic image that described the subsurface geology and composition a in and around the survey area. The overall image quality depends not only on signal sensitivity but also noise effects, contributing to the constant demand for more advanced sensor and receiver technologies.